The present invention relates to systems and materials for presence sensing, and in particular, to a low cost material with magnetizable filaments whose presence may be sensed remotely by an industrial control system to communicate multiple bits of information.
In the manufacture of a multi-component product, for example, packaged pharmaceuticals intended for over-the-counter sale, it is important to verify that the package includes a paper insert listing the characteristics of the drug and instructions for safe use. While considerable care is taken in placing the insert into the package, ideally, its presence in the package could be verified after the package is sealed. One way of doing this is by weighing the package to detect the additional weight of the insert. For light inserts or products that vary in weight, such an approach is unreliable.
The parent to the present application describes a method of verifying the presence of a component of a manufactured product by incorporating a small percentage of filamentized magnetic material into that component whose presence may be detectable at a distance. The filaments are of low cost and may be freely dispersed into the material of the component for manufacturing convenience and may be remotely sensed even through packaging or the like.
While the ability to sense an individual component in a manufactured product is valuable, often it may be necessary to sense combinations of components or to distinguish between different component types. It would be desirable to have a method of communicating not simply presence or absence of a component representing a single binary "bit" of information, but to be able to detect combinations of components and to distinguish between different components such as requires the communication of multiple bits of information.